ABSTRACT There is growing recognition that the first two years of life are a critical period for the prevention of obesity and promising behavioral targets have been identified, including increased intake of fruits and vegetables and decreased intake of sugar-sweetened beverages (SSBs), each of which is associated with parental diet, parental feeding practices, parental perception of infant temperament/behavior and having been breastfed. While the number of behavioral interventions targeting this age group has substantially increased in the last ten years, several critical gaps remain. First, each of the five published trials that focused on the quality of the diet in late infancy delivered multicomponent prevention packages, clouding our knowledge of which intervention strategies were effective. Second, important social changes have not been incorporated into study designs, namely the increased participation of women in the labor force and the convergence of the traditional roles of mothers and fathers; interventions that target mothers and fathers are lacking. Third, mobile technologies have been shown effective at improving a variety of health behaviors among older children and adults, but have been underutilized in existing early life obesity prevention trials. I seek to fill these gaps and become a lead researcher in the field of early life obesity prevention, but require additional training. The NIDDK Mentored Research Scientist Development Award will provide me protected time to seek this training and develop the skills necessary to implement the proposed research. My short-term training goals are to develop scientific and technical skills in: (1) the systematic construction of evidence-based behavioral trials; (2) complex theories of social support; (3) mobile technologies for health interventions (mHealth); and (4) independent, investigator-initiated R-grants. I have developed a strong training plan and mentoring team, which includes leading researchers in each of these areas; researches with demonstrated NIH-funding and extensive mentoring experience. For the research plan, I propose ?Growing Healthy Together,? a mHealth factorial screening experiment that will actively intervene with mothers and fathers and will utilize recent advances in the systematic design of behavioral interventions, which will allow for the isolation of intervention component effects. Using a 24 factorial design, 150 families, stratified on baseline maternal breastfeeding, will be randomized to receive a core intervention of standard nutrition education plus ? 1 of 4 intervention components: 1) text messaging reinforcement and feedback, 2) enhanced intervention engagement via incentives, 3) enhanced partner social support, and/or 4) training in infant behavior. The aims of Growing Healthy Together are to determine the set of intervention components that improve: 1) infant diet at 12 months, 2) change in parent diet between 3-12 months and 3) change in parent responsive feeding style between 3-12 months. Components that improve infant diet, parent diet, or parent feeding style will be included in an optimized intervention package that can be tested in a subsequent randomized controlled trial.